There is an apparatus as an electric power converter having a plurality of DC/DC converters that are connected in parallel to each other disclosed in Japanese Patent Application Laid-Open Publication No. 2002-291247.
In the apparatus according to the Publication No. '247, a series resistance with a resistance value R1 is connected between an output terminal of a first DC/DC converter (output voltage V1) and one of terminals of a load, and similarly, a series resistance with a resistance value R2 is connected between an output terminal of a second DC/DC converter (output voltage V2) and the terminal of the load.
Then, when a load current Io is equal to or less than a threshold value (V1−V2)/R1, the first DC/DC converter is activated, and an output current I1 is outputted.
On the other hand, when the load current Io is exceeding the threshold value, the first and second DC/DC converters are activated, and the output currents I1 and I2 are outputted.
At this time, a difference between the output currents I1 and I2 becomes reduced as the load current Io increases, and when the load current Io becomes Io=(V1−V2)/(R1−R2), the output currents I1 and I2 become I1=I2.
In the above-mentioned electric power converter, in order to improve the reliability and efficiency of the overall electric power converter, it is desirable to control the output current of DC/DC converters to be as equal as possible.
As a method for controlling the output current value of each DC/DC converter equally, a method is considered on which the first and second DC/DC converters are set to a master and a slave, respectively, and operate the slave based on a current command value sent from the master.
However, when using such a method, when a sudden change in the load faster than a communication speed from the master to the slave occurs, the slave is not able to receive the current command value corresponding to the change in the load in time, thus the current that should be outputted is not outputted.
As a result, when it becomes impossible to correspond to the sudden change in the load only by the master, the electric power converter increases or decreases the output current to increase or lower the output voltage depending on the increase or decrease of the load.
Therefore, there is a problem that the output voltage of the electric power converter changes greatly, and thus the electric power converter cannot output a desired power corresponding to the sudden change in the load.